Visual acuity

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major reference

As has been stated, the ability to perceive detail is restricted in the dark-adapted retina when the illumination is such as to excite only the scotopic type of vision; this is in spite of the high sensitivity of the retina to light under the same conditions. The power of distinguishing detail is essentially the power to resolve two stimuli separated in space, so that, if a grating of black...

Although the resolving power of the retina depends, in the last analysis, on the size and density of packing of the receptors in the retina, it is the neural organization of the receptors that determines whether the brain will be able to make use of this theoretical resolving power. It is therefore of interest to examine the responses of retinal ganglion cells to gratings, either projected as...

practice in perceptual learning

...provided by investigating the effects of practice. In so-called detection tasks the observer is required to detect the presence or absence of a selected stimulus. For example, effects of practice on
visual acuity were studied by requiring observers to detect simple orientation (left or right) in a row of leaning letters; e.g., . Practice tended to lower acuity thresholds, defined as the lowest...

test for eye function

...focus on a patient’s symptoms. The ophthalmologist physically examines the eyes with special devices and does various tests to determine visual function. The most important subjective test is for
visual acuity. This is usually performed by having the patient read, from a set distance, an eye chart with a series of letters of graded sizes, which become increasingly smaller as the chart is read...

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